<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0;
            padding: o;

        }
        .box{
            position: relative;
            width: 400px;
            height: 400px;
            border-radius: 200px;
            background: -webkit-radial-gradient(10% 20%,yellow,red,green);
        }
        .box::after{
            display: block;
            content: '';
            position: absolute;
            left: 50%;
            bottom: -100px;
            width: 500px;
            height: 100px;
            border-radius: 50%;
            background-color: grey;
        }
    </style>
</head>
<body>
    <div class="box">

    </div>
</body>
</html>